Rheological and Flowability Characteristics of PET Fibre-reinforced Self-compacting Mortar: Effects of Fibre Geometry and Dosage

The rheological behaviour of Self-Compacting Mortar (SCM) is very sensitive to the addition of various additives. This paper examines the impact of recycled Polyethylene Terephthalate (PET) fibres (obtained from plastic brooms) on the fresh and rheological properties of Self-Compacting Mortar (SCM).

The fibre SCM mix was prepared with four different volume fractions (0.5% to 2.0%) of wavy and linear PET fibres, both having the same length of 20 ± 2 mm. The workability was assessed using the slump-flow and V-funnel tests, and rheological properties were determined using an Anton Paar rotational rheometer.

Flowability decreased as the fibre volume increased, with a maximum decrease of around 8% at 2% fibre volume. An increase in the V-funnel flow time of up to 1.5 seconds was observed, corresponding to an increased resistance to flow between the minimum and maximum fibre content. The rheometer results showed that all mortars followed the Bingham model. The fibres showed little influence on plastic viscosity and yield stress at low fibre dosages, but at high dosages (1.5% and above) the parameters were significantly increased. The wavy fibre showed lower viscosity and improved adaptability to the granular structure of the mortar than the linear fibre.

According to rheometer data, all mixtures complied with the Bingham model; low dosages showed that fibres had no effect on plastic viscosity or yield stress. However, beyond 1.5%, there were noticeable increases, and wavy fibres were shown to be less viscous and better able to adapt to the granular structure than linear fibres.

In conclusion, the use of PET Fibre-reinforced Self-Compacting Mortar (PETF-SCM) exhibits satisfactory fresh workability, rheological properties, and good sustainability, making it a potential candidate for eco-efficient concrete.